Convert Octal to Decimal in Java

We can convert Octal to Decimal in Java in the following ways:

  • Using the parseInt() method
  • Using custom logic

Convert Octal to Decimal in Java using the parseInt() method

Integer class has a method parseInt(String s, int radix) that parses the String argument as a signed integer in the radix specified by the second argument.

Example

class Test {

  public static void main(String[] args) {

    String octalString = "142";

    int decimalNumber = Integer.parseInt(octalString, 8);

    System.out.println(decimalNumber);
  }
}
Output: 98

Parse Octal to Decimal using custom logic

There is always a way without using predefined methods, and that is with custom logic, like in the following example:

class Test {

  public static void main(String[] args) {

    int decimal = getDecimalFromOctal(125);

    System.out.println(decimal);
  }

  public static int getDecimalFromOctal(int octal) {
    int decimal = 0;
    int n = 0;

    while (true) {
      if (octal == 0) {
        break;
      } else {
        int temp = octal % 10;
        decimal += temp * Math.pow(8, n);
        octal = octal / 10;
        n++;
      }
    }
    return decimal;
  }
}
Output: 85
 
That’s it!

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